Automatic by-pass valve



Feb. 13, 1934. HRTH 1,947,040

AUTOMATIC BY- PAS S VALVE Filed Aug. 12; 1929 3 Sheets-Sheet l M Q David f irt/z Feb. 13, 1934. D. FIRTH AUTOMATIC B-Y-PASS VALVE Filed Aug. 12, 1929 3 Sheets-Sheet 2 David Feb. 13, 1934. D. FIRTH AUTOMATIC BY-PAS S VALVE Filed Aug. 12, 1929 3 Sheets-Sheet 3 N12 a" n ("W mDaz/idf t/L '30 It is another object of this invention to provalve 15. The inlet leads to a mixing chamber 85 Patented Feb. 13, 1934 v v I om'reo STATES PATENT OFFICE 1,917,040 AUTOMATIC BY-PASS VALVE i David Firth, Flint, Mich, assignor to Marvel Carburetor 00., Flint, Mich., a. corporation of IllillOlS Application August 12, 1929. Serial No. 885,195

6 Claims. (Cl. 12s 119) This invention relates to priming or starting the carburetor, showing the choke valve linkage devices for internal combustion engines adapted controlling the byp i to supply a rich starting mixture at low cranking re 3 s a ra me te s io O the li speeds. III-III of Figure 1, showing the bypass and valve 5 It is an object of this invention to provide an of this invention.

improved and simplified automatic primer to Figured is a fra e e ect on im ar to that assist in starting an engine as well as to keep of Figure 3 wherein the y a Valve is shown in an engine running during the warmingup period its Op positionshould it tend to stop due to an insuflicient idling Fi ur 5 s a raern tal s ti n on the line i 10 fuel supply resulting from cold starting condi- V-V f ure 3,

tions. To this end I have provided an idling s shown on the drawings! bypass around the carbureter throttle that is con- One embodiment of t e w is shown a trolled by a suction actuated automatic valve so i p at d in a carburetor o h air valve yp proportioned as to open the bypass for moderately which is secured-to a jacketed manifold riser 10 15 trong manifold suctions uch 3,5 are set, up by containing the usual thlOttlB valve 11. This parslow cranking speeds, but which valve is adapted a arrangement is not important in n to be closed by the extreme manifold suction tiOn With the Present invention wherein a ypa created by a properly idling engine. with thi passage 12 has its outlet 13 into the riser above arrangement the cranki speed i t, great the throttle location which may be varied in enough to cause sufficient suction to close the location Without in y Way effecting the p valve so that starting is assisted by the bypass of poses of this invention except that the thmttle a'rich fuel mixture under such conditions, while location determines the Position of h bypa 'W n h en ine is operating under'idling condioutlet, which must be subjected to the manifold tions the .suction is sufficient-to close the valve suction as distinguished f m t e earbureter ene- 25 and thus out ofi the bypassed fuel upply, If tiOIl, as the variation Of the manifold suction the engine has been started and tends to stop p a es the bypass valve, as W ll hereinafter again, the suction drops and the bypass valve e fully app n. opens again so that the engine is enabled to pick The essential parts of buret r shown up speed instead of stalling. comprise an air inlet 14 controlled by a choke vide an improved and simplified automatic by- 16, P a flap air Valve 17 pivoted at and pass arrangement for delivering fuel, from the Closed by a n 19 carrying a Piston backed usual idling fuel nozzle, above the throttle when y a spring 21 a chamber 22 which acts as a the suction within the carburetor is insuflicient dash p t. The pas e back or to t e r ht f 3 to create and deliver a satisfactory fuel and air the pivot 18 is closed by a member 23 containing mixture through the normal carbureter passages. a small Venturi shaped passage 24. A low speed It is also another object of'this invention to fuel nozzle 25 is positioned at the throat of the provide means associated with the-usual choke t ri nd i supplied with fuel through pas-- valve for a nta the byp p as long as sages 26 and 2'7 leading from a float chamber 28. 40 the choke valve is closed in order to maintain the Th b ass passage 12 is formed in the wall engine speed a y high while warming up a c d of the carburetor body and has a side inlet port engine. i 29 opening into the mixing chamber immediately Othe and urth important eblects Of this above and to one side of the member 23 so that vention will be apparent from thedisclosures in th bypass passage tends to draw a, rich fuel and the specification and the accompanying drawings. air mixture from the Venturi passage 24 and 1 This invention (in a Preferred form) i nozzle 25. The lower end of the passage 12 adtrated in the drawings and hereinafter more fully t' th t 29 i enlarged to form a valve described. chamber 30 the lower end of which is closed by 50 On the drawings v a plug 31. The shoulder 32 at the upper limit Figure 1 is a e t a se t e through a of the chamber 30 forms a valve seat cooperathureter and a portion of the intake manifold riser, ing with a tapered neck 33 on a valve 34, an upshowing a bypass passage embodying the features ward extension of the neck being formed as a of this invention. polygonal valve centering guide 35 without ob- 55 Figure 2 is an elevation of the reverse side of structing the passage of a fuel and air mixture. 1

The valve 34 carries a lower outstanding flange 36 against which one end of a spring 3'7 abuts, the other end of the spring bearing against the I chamber shoulder 32.

This spring serves to move the valve as a whole away from its seat, while suction in the passage 12 tends to pull the valve up to its seat to close the bypass, acting against the spring pressure.

By a proper calibration of the spring, the valve suction of about 12 inches of mercury, then the valve will open to bypass an additional supply;

of fuel to permit the engine to pick up speed again.

For starting in cold weather, the cranking speed is not great enough to cause sufficient suction to close the valve against such a spring pressure, so that thevalve remains open and supplies a richfuel and air mixture to the manifold above a closed throttle. If the throttle ispartially or wholly open the bypass ceases to function regardless of the degree of suction as in such a case the pressure is substantially equalized above and below the throttle and a direct passage through the carbureter'is provided for the fuel and air mixture discharged by the venturi 24. A partial equalization of pressure above and below the throttle reduces the differential suction acting on the valve to a point below the spring value, but the bypass does not function to deliver fuel because of the direct path provided therefor within the carbureter proper.

The choke valve 15 is operated by a double armed lever 38 onearm 39 of which has a link 40 extending to a lever4l on a stub shaft 42 carrying a cam 43 in .the chamber 30 in a position toengage the valve flange 36 to hold the same downwardly with the valve open, when the choke valve is partially or completely closed. With this arrangement, the bypass valve is prevented. from closing when the choke valve is in use, thus supplying additional mixture to the engine which. allows the engine speed to be kept fairly high during' the warming up period as long improved and simplified automatic primer which will not only assist in starting a slowly cranked engine but will automatically function to admit additional fuel, should the engine slow down to stalling speed, thus permitting the engine to pick up speed again instead of stopping.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, there-' fore do not purpose limiting the patent granted hereon otherwise than necessitated by the prior I claim as myinvention: I

1. In combination with'a carbureter, a choke valve, and a throttle valve therefor, a bypass passage around said throttle valve location, the discharge end of said passage being subjected to the suction above the throttle while the inlet end of said passage is positioned adjacent the normal carbureter mixture producing arrangements to draw a fuel and air mixture therefrom, an automatic valve so positioned in said bypass passage as to be closed by extreme suction therein, and means operated in unison with the choke valve for preventing the closing of said automatic valve upon a partial closure of said choke valve.

2. In combination with a carbureter, a choke valve, and a throttle valve therefor, a bypass passage around said throttle valve location, the discharge end of said passage being subjected to the suction above the throttle while the inlet end of said passage is positioned adjacent the normal carbureter mixture producing arrangements to draw a fuel and air mixture therefrom, an automatic valve so positioned in said bypass passage as to be closed by extreme suction therein, a spring for opening said valve against the suction in said passage, and means operated in unison with the choke valve for preventing the closing of said automatic valve upon a partial closure of said choke valve.

3. In combination with the choke valve, throttle and mixture producing device of a carbureter, a bypass passage leading from said mixture producing device to the engine side of said throttle whereby the bypass passage is at all times subjected to the varying degrees of suction created by the engine, suction responsive means in said passage for closing the same at high suctions, and means operated by said choke valve for maintaining said suction responsive means open upon a partial closure of said choke valve.

4. In combination with the choke valve, throttle and mixture producing device of a carbureter, a bypass passage leading from said mixture producing device to the engine side of said throttle whereby the bypass passage is at all times subjected to the varying degrees of suction created by the engine, suction responsive means to said passage for closing the same at high suctions, means yieldingly opposing the closing of said suction responsive means, and means operated by said choke valve for maintaining said suction responsive means open upon a partial closure of said choke valve.

5. In combination with a. carbureter and the throttle valve thereof, a fuel and air mixture passage bypassing around said throttle, an automatic suction responsive valve for. closing said passage, and choke controlled means for opening 

